I have been using Diigo for several years and installed the extension about two years ago. This is an absolutely amazing tool that allows me to manage web sites and document web sites, add tags and organize this information , highlight and annotate and keep all of this readily available online for use on any device, including my SmartPhone. The extension has been improved over time and made even better. I only wish I could give Diigo a 10 star rating. I would recommend this app and extension to Firefox to anyone.